Our body uses several defense mechanisms against seasonal flu, the common affliction caused by influenza viruses. By taking a yearly flu shot, our body's defense based on antibodies is trained and envoked. A defense system not based on antibodies acts at the very front line of influenza virus attack, namely the lungs. For this protection the body uses so-called lung surfactant proteins that coat the inner lining of the lungs to keep a wet film on the lung surface needed for oxygen-carbon dioxide exchange. The lung surfactant proteins also serve as police against influenza viruses. For this purpose the lung surfactant protein D (SP-D) recognizes a protein component of the virus surface, namely hemagglutinin, and handcuffs the sugar molecules bound to hemagglutinin. A previous experimental-simulation study (see October 2012 highlight) found that SP-D of pigs exhibits a stronger inhibitory activity against influenza A virus in this regard than does human SP-D. In a recent study, researchers have now boosted the protective ability of human SP-D by introducing mutations. Molecular dynamics simulations using NAMD suggest that the mutated human SP-D employs a different and stronger blocking mechanism on the active site of influenza A virus than native SP-D does. Combined with experimental results, the simulations suggest a mechanism through which SP-D acts, namely, by handcuffing viruses together and, thereby, preventing viral entry into cells. The findings from this research might lead to a new protection against seasonal flu, namely a nasal spray containing mutated lung surfactant proteins that strengthen a person's armada of defense proteins on the lung surface. More on our lung surfactant protein website.